LEDs (Light Emitting Diode) are used in a variety of applications as indicator lamps and in different types of lighting environments, for example in aviation lighting, digital microscopes, automotive lighting, backlighting, advertising, general lighting, and traffic signals. The LEDs have significant advantages such as high efficiency, good directionality, color stability, high reliability, long life time, small size, and environmental safety. The LED systems having efficient power factor leads to various factors such as less thermal runaway issues, less chances of flicker and less fault scenarios. Power factor is defined as the ratio of real power to apparent power. Power factor correction (PFC) is the process of adjusting the characteristics of electric loads that create a power factor less than 1. Power factor correction is used to improve the stability and efficiency of the transmission network. The power factor correction inturn reduces the costs in the transmission networks by reducing the losses. A high power factor (i.e., close to unity, or “1”) is generally desirable in a transmission system to reduce transmission losses and improve voltage regulation at the load.
Various types of conventional LED circuits that are used for active power factor correction are known in the prior art. The U.S. Pat. No. 7,952,293 B2describes the power factor correction and driver circuits. The claimed circuit defines about the power factor correction and driver circuits. Driver circuits configured for electrical loads such as series arrangements of light emitting diodes are also described. An exemplary embodiment of a driver circuit can implement a comparator and/or a voltage regulator to allow for improved output current uniformity for high-voltage applications and loads, such as series configurations of LEDs. Embodiment of PFC stages and driver stages can be combined for use as a power supply, and may be configured on a common circuit board. Power factor correction and driver circuits can be combined with one or more lighting elements as lighting.
The U.S. Pat. No. 7,295,452 B1 describes an active power factor correction circuit and control method thereof. The method comprises the following steps. Drive the power switch of the circuit so that the average inductor current waveform follows the rectified input voltage waveform. Suspend the operation of the power switch at a first moment in a first line cycle of the rectified input voltage and then resume the operation of the power switch at a second moment in a second line cycle of the rectified input voltage. The first moment is when the phase angle of the rectified input voltage exceeds a predetermined angle and the switching frequency of the power switch exceeds a predetermined frequency. The time span from the first moment to the end of the first line cycle is substantially as long as the time span from the beginning of the second line cycle to the second moment.
However, the claimed driver circuits and methods use analog and digital implementations. The analog implementations use external elements such as capacitors to estimate the average current and to achieve low loop band width for PFC. The driver circuit uses external components to detect accurate switching cycle by cycle power for open loop LED driver application. The digital implementations use expensive filter implementations and/or complicated high speed sampling schemes. These implementations does not provide enough flexibility to detect switching cycle by cycle power, loop band width adjustability, error detection etc.
Typically, the Switching Mode Power Supply (SMPS) does not receive continuous power from input supply, which leads to Low Power Factor (LPF) and THD. The passive PF scheme minimises the THD and improves the PF by drawing continues power from the input supply. However, the passive scheme leads to increased component count, cost, lower efficiency and board space requirements.
Typically, in convention PFC the wave shaping implies to higher currents at higher AC Supply and lower currents at lower supply, which leads in higher peak (inductor) currents and lower efficiency. The approach requires higher current rated inductors, which results in increased cost.
Hence, there is need for a system and method to achieve optimal balance between current accuracy, PF, THD and peak inductor currents using the active PFC without the use of external components therein. Further, the system achieves PFC through customized wave shaping profile by using the intelligent current control and peak current limit control, customizable through a firmware.